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United States Patent |
6,151,956
|
Takahashi
,   et al.
|
November 28, 2000
|
Oil deterioration sensor
Abstract
The present invention relates to a sensor for detecting the degree of
deterioration of oil, and more particularly, provides an oil deterioration
sensor which can detect the deterioration of oil and/or the liquid surface
of oil by utilizing the fact that the sound velocity of ultrasonic waves
change according to the alkalinity of the oil, the oil deterioration
sensor for determining deterioration characteristics of oil by utilizing
ultrasonic waves, which is characterized in that a deterioration sensor
reflecting surface for reflecting ultrasonic waves transmitted from an
ultrasonic wave transmitting portion is placed in oil so as to detect
deterioration of the oil, and characterized by comprising: an oil
deterioration detecting portion for evaluating a transmission velocity of
an ultrasonic wave in the oil by receiving ultrasonic waves from the
aforesaid deterioration sensor reflecting surface and for evaluating a
degree of deterioration of oil from said transmission velocity of the oil.
Inventors:
|
Takahashi; Toshimitsu (Susono, JP);
Kondo; Takuya (Susono, JP)
|
Assignee:
|
Toyota Jidosha Kabushiki Kaisha (Toyota, JP)
|
Appl. No.:
|
148508 |
Filed:
|
September 4, 1998 |
Foreign Application Priority Data
Current U.S. Class: |
73/53.05; 73/10; 73/32A; 73/54.41; 73/61.49 |
Intern'l Class: |
G01N 003/56; G01N 009/24; G01N 033/26; G01N 029/18 |
Field of Search: |
73/53.05,54.41,61.49,32 A,10
|
References Cited
U.S. Patent Documents
3859846 | Jan., 1975 | Asadia et al. | 73/53.
|
4320659 | Mar., 1982 | Lynnworth et al. | 73/54.
|
4565088 | Jan., 1986 | Crambes | 73/61.
|
4779452 | Oct., 1988 | Cohen-Tenoudji et al. | 73/54.
|
4827746 | May., 1989 | Kawaguchi | 73/32.
|
5060507 | Oct., 1991 | Urmson et al. | 73/597.
|
5255564 | Oct., 1993 | Glad et al. | 73/597.
|
5271267 | Dec., 1993 | Baumoel | 73/54.
|
5739432 | Apr., 1998 | Sinha | 73/61.
|
5886262 | Mar., 1999 | Sinha | 73/579.
|
5907278 | May., 1999 | Park et al. | 73/53.
|
5987972 | Nov., 1999 | Hirota et al. | 73/61.
|
Foreign Patent Documents |
7-225228 | Aug., 1995 | JP.
| |
Other References
Susumu Sakagami, et al., Proceeding of the Scientific Meeting, No. 952, pp.
199 to 202, "Fuel Property Detection Using Fuel Density", May 1995 (with
partial English translation).
|
Primary Examiner: Williams; Hezron
Assistant Examiner: Soliz; Chad
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier & Neustadt, P.C.
Claims
We claim:
1. An oil deterioration sensor which can distinguish deterioration
characteristics or a liquid surface of oil by utilizing ultrasonic waves,
characterized in that a deterioration sensor reflecting surface for
reflecting ultrasonic waves transmitted from an ultrasonic wave
transmitting portion is placed in oil so as to detect deterioration of the
oil, and comprising: an oil deterioration detecting portion for detecting
a transmission velocity of an ultrasonic wave in the oil by receiving
ultrasonic waves from said deterioration sensor reflecting surface and for
determining a base number of the oil as a measure of a degree of
deterioration of oil from said transmission velocity of the oil; and an
oil level detecting portion for transmitting ultrasonic waves from said
ultrasonic wave transmitting portion to an air-liquid liquid surface of
the oil and for detecting a height of said liquid surface by receiving
ultrasonic waves from said liquid surface.
2. The oil deterioration sensor according to claim 1, wherein a
piezoelectric-crystal element, whose temperature characteristics abruptly
change at a predetermined temperature, is used in the sensor element.
3. The oil deterioration sensor according to claim 1 or 2, wherein said
sensor is used for determining the kind of oil from the transmission
velocity of the ultrasonic wave.
4. The oil deterioration sensor according to claim 1, wherein the
ultrasonic waves are transmitted and received independently.
5. The oil deterioration sensor according to claim 1, wherein the
ultrasonic reflecting wave from the deterioration sensor reflecting
surface is received by a transducer at a transmitting side thereof, and
the ultrasonic reflecting wave from the liquid surface of oil is received
by a receiving-only transducer.
6. The oil deterioration sensor according to claim 1, wherein the
reflecting ultrasonic waves from the deterioration sensor reflecting
surface and the liquid surface of oil are received by only one transducer.
7. An oil deterioration sensor for determining deterioration
characteristics of oil by utilizing ultrasonic waves, comprising a sensor
element positioned to measure the transmission velocity of ultrasonic
waves in oil by transmitting and receiving ultrasonic waves in the oil,
and means for determining a base number of the oil as a measure of a
degree of deterioration of the oil from the measured transmission velocity
of ultrasonic waves.
8. The oil deterioration sensor of claim 7, wherein the sensor element
comprises a piezoelectric-crystal element having output characteristics
which abruptly change at a predetermined temperature.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a sensor for detecting the
degree of deterioration of oil, and more particularly, to an oil
deterioration sensor being capable of detecting deterioration of oil
and/or an oil level by utilizing the fact that the sound velocity of an
ultrasonic wave varies with the alkalinity of oil.
2. Description of the Prior Art
Lubrication functions of engine oil for automobiles deteriorate owing to
the deterioration of the oil itself, to combustion products of a fuel, and
to dust, moisture and abrasion powder contained in intake air. Therefore,
oil itself requires oxidation stability, acid corrosion-resistance and the
suppression of generation of water and bubbles. A base number (namely, a
total base number) serving as an index concerning various additives, which
indicates an oil characteristic, is also an index to total basic
components or ingredients, which is represented by an amount of potassium
hydroxide needed for the neutralization of basic components contained in
the oil. This index is effective in evaluating or determining the degree
of deterioration of oil.
It is known that, especially in the case of engine oil for automobiles,
such a base number controls the acid neutralization, which is employed as
an engine-oil characteristic, and the oil deterioration characteristics,
such as cleanliness, of engine oil. Hitherto, regarding the measurement of
the density of gasoline for automobiles, for example, the Japanese
Unexamined Patent Publication (Kokai) No. 7-225228 has disclosed the
techniques of measuring a delay time to the transmission of an ultrasonic
wave signal from an ultrasonic sensor, and then calculating the density of
a fuel from this delay time and finally distinguishing the property
thereof from this density.
However, the detection of the degree of deterioration of engine oil by the
methods of measuring a delay speed of propagation of an ultrasonic wave
has never been conducted. Even if it is intended to adopt such
conventional methods, in the case that the deterioration of engine oil is
detected from the strength of a reflected wave, the strength of the
reflected wave is reduced when air bubbles are mixed in the oil. Thus, a
detection error is caused. Consequently, it is substantially impossible to
adopt the aforementioned conventional methods. Further, the temperature of
the oil rises after an engine is started. Thus, the sound velocity of an
ultrasonic wave changes. Consequently, in the case of the aforementioned
techniques using ultrasonic waves, there is the necessity for using a
high-precision thermometer that excels in response and resolution.
Moreover, the equipment cost rises. Thus, there are such problems for the
practical application of such conventional techniques. Therefore, the
development of a sensor which utilizes ultrasonic waves as a relatively
simple or convenient means for measuring the degree of deterioration of
engine oil and has high responsibility and is advantageous in terms of the
cost, has been desired.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an oil deterioration
sensor for determining the degree of deterioration of engine oil from the
fact that the sound velocity changes according to the alkalinity of the
oil, by utilizing ultrasonic waves in a sensor for determining the degree
of deterioration of oil.
Further, another object of the present invention is to provide an oil
deterioration sensor which can achieve the measurement of the degree of
deterioration of oil and/or the detection of the liquid surface of the oil
according to ultrasonic waves transmitted from at least one transducer, by
utilizing ultrasonic waves, which is a relatively simple and convenient
means for the measurement of the degree of deterioration of the oil and/or
the detection of the liquid surface of the oil.
Furthermore, still an object of the present invention is to provide an oil
deterioration sensor which can correct the sound velocity of the
aforementioned ultrasonic wave through the utilization of a transducer,
whose characteristics greatly change with temperature, by utilizing a
method of enhancing the precision in measuring the sound velocity which is
significantly affected by temperature.
The gist of the present invention is summarized as follows:
(1) An oil deterioration sensor for determining deterioration
characteristics of oil by utilizing ultrasonic waves, characterized in
that the transmission velocity of ultrasonic waves in oil is measured by
transmitting and receiving ultrasonic waves in the oil, and that a degree
of deterioration of the oil is detected from said transmission velocity of
ultrasonic waves.
(2) An oil deterioration sensor which can distinguish deterioration
characteristics or a liquid surface of oil by utilizing ultrasonic waves,
characterized in that a deterioration sensor reflecting surface for
reflecting ultrasonic waves transmitted from an ultrasonic wave
transmitting portion is placed in the oil so as to detect deterioration of
the oil, and comprising: an oil deterioration detecting portion for
detecting a transmission velocity of an ultrasonic wave in the oil by
receiving ultrasonic waves from said deterioration sensor reflecting
surface and for detecting a degree of deterioration of oil from said
transmission velocity of the oil; and an oil level detecting portion for
transmitting ultrasonic waves from said ultrasonic wave transmitting
portion to a liquid surface of the oil and for detecting a height of said
liquid surface by receiving ultrasonic waves from said liquid surface.
(3) The oil deterioration sensor according to item (1) or (2), wherein a
piezoelectric-crystal element, whose temperature characteristics abruptly
change at a predetermined temperature, is used in the transducer.
(4) The oil deterioration sensor according to item (1) or (2), wherein said
sensor is used for determining the kind of oil from the transmission
velocity of the ultrasonic wave.
(5) The oil deterioration sensor according to item (2), wherein the
ultrasonic waves are transmitted and received independently in the oil
deterioration sensor reflecting surface and the liquid surface of oil.
(6) The oil deterioration sensor according to item (2), wherein the
ultrasonic reflecting wave from the deterioration sensor reflecting
surface is received by a transducer at the transmitting side, and the
ultrasonic reflecting wave from the liquid surface of oil is received by a
receiving-only transducer.
(7) The oil deterioration sensor according to item 2, wherein the
reflecting ultrasonic waves from the deterioration sensor reflecting
surface and the liquid surface of oil/are received by one transducer.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 a diagram for showing an outline of a sensor and an apparatus of
Example 1 according to the present invention.
FIGS. 2(a) and 2(b) show ultrasonic waves transmitted and received by the
sensor according to Example 1; FIG. 2(a) is a diagram showing a
deterioration sensor; and FIG. 2(b) is a diagram showing an oil level
sensor.
FIG. 3 is a diagram for showing an outline of a sensor and an apparatus
according to Example 2 of the present invention.
FIGS. 4(a)-4(c) show ultrasonic waves transmitted and received by the
sensor according to Examples; FIG. 4(a) is a diagram showing a
deterioration sensor of Example 2; FIG. 4(b) is a diagram showing
ultrasonic waves received from an oil level sensor of Example 2; and FIG.
4(c) is a diagram showing a deterioration sensor and an oil level sensor
of Example 3;
FIGS. 5(a)-5(c) show a sensor and an apparatus according to example of the
present invention; FIG. 5(a) is a diagram showing an outline of one
transducer; FIG. 5(b) is a diagram showing an outline of a transducer
adapted to transmit ultrasonic waves upwardly and downwardly; and FIG.
5(c) is a diagram showing an outline of a sensor in the case that the
strength of ultrasonic waves reflected from the liquid surface of oil is
increased.
FIGS. 6(a) and 6(b) show a sensor, an apparatus and ultrasonic waves
transmitted and received in Example 4 according to the present invention;
FIG. 6(a) is a diagram showing an outline of the apparatus; and FIG. 6(b)
is a diagram showing ultrasonic waves transmitted and received by a
transducer thereof.
FIGS. 7(a) and (b) show sound-velocity propagation characteristic of
ultrasonic waves in oil according to the present invention; FIG. 7(a) is a
diagram showing the relationship between the sound velocity thereof and
temperature; and FIG. 7(b) is a diagram showing the relationship between
the total base number and the sound velocity.
FIGS. 8(a)-8(c) show the temperature characteristics of oil according to
the present invention; FIG. 8(a) is a diagram showing a change in
temperature of the oil; FIG. 8(b) is a diagram showing the temperature
characteristics of a piezoelectric-crystal element; and FIG. 8(c) s a
diagram showing the resistance characteristics of a thermistor.
FIGS. 9(a) and 9(b) illustrate Example 5 of the present invention; FIG.
9(a) is a diagram showing an outline of an apparatus thereof; and FIG.
9(b) is a diagram showing the relationship between the value of the sound
velocity in oil and the oil type.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In the case of the first and second oil deterioration sensors of the
present invention, the sound velocity of ultrasonic waves changes
according to the alkalinity of oil, which reflects the deterioration of
the oil. Thus, the deterioration of the oil can be detected by measuring
this sound velocity. Further, both of the oil deterioration and the oil
level can be simultaneously detected or determined by receiving ultrasonic
waves reflected from the oil surface. Moreover, the sound velocity of
ultrasonic waves varies with temperature and thus should be measured at a
predetermined temperature. However, the need for a thermometer is
eliminated by employing the constitution of the third oil deterioration
sensor of the present invention.
The inventors of the present invention have accomplished the present
invention by acquiring the following knowledge by an experiment. Engine
oil exhibits the propagation characteristics of ultrasonic waves therein
as illustrated in FIGS. 7(a) and 7(b). Namely, as shown in FIG. 7(a), the
sound velocity linearly decreases with the rise in temperature. This
figure shows changes in the sound velocity, which respectively correspond
to two different kinds of oil, No. 1 and No. 2.
On the other hand, according to the relationship between the total base
number and the sound velocity in No. 3 oil as illustrated in FIG. 7(b),
the sound velocity rises with the decrease in the total base number. In a
range where the total base number is nearly 2 or less, this relationship
tends to become more pronounced. However, this relationship can be
represented by a nearly fixed or constant relation, on the average. The
relations illustrated in these figures enable the sensor to detect and
judge the degree of deterioration of oil by first correcting an actual
measured value of the sound velocity to a value of the sound velocity at a
certain temperature and by then finding a total base number corresponding
to the sound velocity at the standard temperature at that time.
After the correction at that time, the sound velocity rises with the
progress of deterioration of the oil. This is because, as is understood
from the following expression; C=(K/.rho.) where C denotes the sound
velocity; K a volume elasticity; and .rho. a density, the viscosity of the
oil changes owing to the ablation of an oil additive and to the
degradation of base oil. As a result, the volume elasticity rises. In
other words, the sound velocity rises with reduction in the total base
number which is an index of oil deterioration.
Next, a method of measuring temperature by using a piezoelectric element,
whose temperature characteristics drastically change in a specific
temperature region, according to the present invention will be described
hereinbelow with reference to FIGS. 8(a), 8(b) and 8(c).
As shown in FIG. 8(a), the temperature of the oil rises with time after an
engine is started. Hitherto, a high-precision thermometer that excels in
responsiveness and resolution has been needed for measuring temperature in
a region where a change in temperature is large. However, if the sound
velocity can be measured in a stable temperature range where this change
in temperature is small, for instance, in the vicinity of 80.degree. C. in
the case of a normal operation mode, the influence of the change in
temperature can be disregarded. Further, the sound velocity can be
measured with good precision.
The high-accuracy measurement of temperature in a region, in which a change
in temperature is small, can be achieved without providing a thermometer
in the apparatus, by using a material whose impedance (or resonance
frequency) largely changes with temperature in the aforementioned
sound-velocity measuring temperature range as illustrated in FIG. 8(b).
Furthermore, the high-accuracy measurement of temperature can be attained
by using a thermistor, whose resistance characteristics rapidly change in
the proximity of a sound-velocity measuring temperature, to be employed as
a semiconductor whose resistance largely changes according to temperature,
for example, a PCT (polychlorinated terphenyl) thermistor which is usually
employed in a temperature switch. In this case, simultaneously, the cost
is considerably reduced. Additionally, the sensor of the present invention
can be also used as a gasoline characteristic sensor and a gasoline level
sensor, by inserting it into a gasoline tank.
Hereinafter, the present invention will be further described, in detail,
with reference to the examples.
EXAMPLES
Example 1
This example of the present invention relates to an engine oil level/oil
deterioration sensor and is adapted to transmit ultrasonic waves into oil
and to receive ultrasonic waves reflected from a deterioration sensor
reflecting surface and an oil surface.
FIG. 1 shows an outline of a device of this embodiment. An ultrasonic wave
transmitting/receiving portion 3 of a transducer is provided in oil
contained in an oil pan 5. As viewed in this figure, the ultrasonic wave
transmitting/receiving portion transmits ultrasonic waves perpendicularly
to the deterioration sensor reflecting surface 2 and the oil surface 1,
respectively, independent of each other. Then, the ultrasonic wave
transmitting/receiving portion receives ultrasonic waves reflected
therefrom. Further, data representing a measured propagation time is
inputted to a propagation time measuring circuit 7. Thereafter, data is
outputted therefrom as data representing the results of measurements
respectively performed by an oil level measurement portion 9 and a sound
velocity measurement portion 10. Subsequently, oil temperature information
is inputted by a temperature sensor 4 to a temperature measuring circuit
8. Then, the oil level and the sound velocity value are corrected
according to the temperature indicated by the oil temperature information.
FIG. 2(a) shows ultrasonic waves reflected in a typical deterioration
sensor side transducer. FIG. 2(b) shows ultrasonic waves reflected at a
typical oil surface side transducer. Namely, in the case of this
embodiment, a result of the detection or determination of oil
deterioration is obtained by measuring the sound velocity of ultrasonic
waves, which are reflected on the reflecting surface of the deterioration
sensor and return to the ultrasonic wave transmitting/receiving portion in
oil. Further, a result of the determination of the oil level is obtained
by finding the values of the sound velocity and the propagation time from
ultrasonic waves, which are reflected on the oil surface and return to the
ultrasonic wave transmitting/receiving portion, in oil and by determining
or measuring the distance between this portion and the oil surface from
such values of the sound velocity and the propagation time.
Example 2
This example is a sensor obtained as a modification of Example 1 by
employing a single transducer instead of two ultrasonic wave transmitting
transducers in Example 1. In the case of Example 2, some of the ultrasonic
waves transmitted from the transducer, which are reflected by the
reflecting surface of the deterioration sensor, are received by the
transmitting transducer, while the other part of the ultrasonic waves
transmitted from the transducer, which are reflected by the boundary
surface (namely, the liquid surface) between the oil and air, are received
by a receive-only transducer.
FIG. 3 shows an outline of the device according to this example. Ultrasonic
wave transmitting/receiving portions of the transducers 13 and 14 are
obliquely provided in the oil. As shown in this figure, ultrasonic waves
are simultaneously transmitted to the deterioration sensor reflecting
surface 2 and the oil surface 1 from a direction inclined to a vertical
direction. Further, ultrasonic waves reflected from the reflecting surface
2 and the oil surface 1 are respectively received by transducers 13 and
14, independent of each other. Thus, the transducer 14 is a receive-only
transducer. FIG. 4(a) shows ultrasonic waves reflected at a typical
deterioration sensor transducer. FIG. 4(b) shows ultrasonic waves
reflected at a typical oil surface transducer. Namely, in the case of this
embodiment, a result of the detection of oil deterioration is obtained by
measuring the sound velocity of ultrasonic waves, which are reflected on
the reflecting surface of the deterioration sensor and return to the
ultrasonic wave transmitting/receiving portion, in the oil. Further, a
result of the determination of the oil level is obtained by finding the
values of the sound velocity and the propagation time from ultrasonic
waves, which are reflected on the oil surface and return to the ultrasonic
wave receiving transducer 14 in the oil, and by measuring the distance
between this portion and the oil surface from such values of the sound
velocity and the propagation time.
Example 3
In the case of a sensor of this example, a single transducer serves both as
the deterioration sensor transducer and the oil surface transducer.
FIGS. 5(a), 5(b) and 5(c) show an outline of a device or sensor of this
example. In the case of the device of FIG. 5(a), a transducer 3 is
provided with a deterioration sensor reflecting plate 2 whose diameter is
almost 1/2 of that of a transducer 3 or less. Further, in the case of the
device of FIG. 5(b), each of transducers 3a and 3b may be of the two-piece
type or may be a single transducer of the type that can radiate ultrasonic
waves from both sides thereof. Moreover, each of the transducers 3a and 3b
can transmit ultrasonic waves from both sides thereof. Furthermore, the
sensor is provided with a deterioration sensor reflecting plate 2 on the
bottom surface side. In this case, the outside diameter of the sensor can
be decreased. In the case of the device of FIG. 5(c), each of transducers
3a and 3b can transmit ultrasonic waves from both sides thereof, similarly
as in the case of the device of FIG. 5(b). Further, the sensor is provided
with a deterioration sensor reflecting plate 2. Furthermore, a float 16 is
provided at the liquid surface side of the sensor. Additionally, a
reflecting plate 15 is provided on the bottom surface of the float 16. In
this case, the strength of ultrasonic waves reflected from the liquid
surface can be enhanced by immersing the reflecting surface mounted on the
float in the oil.
In all cases, ultrasonic waves respectively transmitted perpendicularly
from a transducer are reflected by the deterioration sensor reflecting
plate and the liquid surface independently of each other and are received
by a same transducer. FIG. 4(c) shows ultrasonic waves reflected at a
typical deterioration sensor side transducer and at a typical oil level
sensor side transducer. Namely, in the case of this example, a result of
the detection or determination of oil deterioration is obtained by
measuring the sound velocity of ultrasonic waves, which are reflected on
the reflecting surface of the deterioration sensor and return to the
ultrasonic wave transmitting/receiving portion, in the oil. Further, a
result of the determination of the oil level is obtained by finding the
values of the sound velocity and the propagation time from ultrasonic
waves which are reflected on the oil surface and return to the ultrasonic
wave transmitting/receiving portion in the oil and by determining the
distance between this portion and the oil surface from the values of the
sound velocity and the propagation time.
Example 4
This example of the present invention relates to an engine oil
deterioration sensor and is adapted to transmit ultrasonic waves into oil
and to receive ultrasonic waves reflected from a deterioration sensor
reflecting surface.
FIG. 6(a) shows an outline of a device of this example. This device has a
constitution consisting of a transducer for transmitting and receiving
ultrasonic waves, a temperature sensor for measuring the temperature of
oil at the time of sensing, a reflecting surface for maintaining the
propagation distance of ultrasonic waves at a constant value, and an
electronic circuit portion for measuring a propagation time.
Practically, the ultrasonic wave transmitting/receiving portion of the
transducer 3 is provided in an oil 6 that is contained in an oil pan 5. As
viewed in this figure, the ultrasonic wave transmitting/receiving portion
transmits ultrasonic waves perpendicularly to the deterioration sensor
reflecting surface 2. Then, the ultrasonic wave transmitting/receiving
portion receives ultrasonic waves reflected therefrom. Further, data
representing a measured propagation time is inputted to a propagation time
measuring circuit 7. Thereafter, data is outputted therefrom as data
representing results of measurements performed by a sound velocity
measurement portion. Subsequently, oil temperature information is inputted
by a temperature sensor 4 to a temperature measuring circuit 8 and a
temperature correcting circuit 11. Then, the sound velocity value is
corrected according to the temperature indicated by the oil temperature
information. Further, the degree of deterioration of the oil is determined
or judged.
FIG. 6(b) shows ultrasonic waves reflected at a typical deterioration
sensor side transducer. Namely, in the case of this embodiment, the result
of the detection or determination of oil deterioration is obtained by
measuring the sound velocity of ultrasonic waves, which are reflected on
the reflecting surface of the deterioration sensor and return to the
ultrasonic wave transmitting/receiving portion, in the oil. Then, the
temperature correction is performed on the sound velocity so that the
sound velocity is changed into the value of the sound velocity at a
reference temperature. After the correction, the sound velocity rises with
the progress of deterioration of the oil. Thus, a judgement on the
deterioration of the oil can be made.
According to the relationship between the total base number and the sound
velocity in the oil as illustrated in FIG. 7(b), the sound velocity rises
with a decrease in the total base number. In a range where the total base
number is nearly 2 or less, this relationship tends to become more
pronounced. However, this relationship can be represented by a nearly
constant relation, on the average. The relations illustrated in these
figures enable the sensor to detect and judge the degree of deterioration
of oil by first correcting an actual measured value of the sound velocity
into the value of the sound velocity at a certain temperature and by then
finding a total base number corresponding to the sound velocity at the
standard temperature at that time.
After the correction at that time, the sound velocity rises with the
progress of deterioration of the oil. This is because the viscosity of the
oil changes owing to the ablation of an oil additive and to the
degradation of the base oil, as is understood from the aforementioned
expression representing the sound velocity, and consequently, the volume
elatisticity rises. In other words, the sound velocity rises with
reduction in the total base number which is an index of oil deterioration.
Thus, no sound-velocity change is caused due to bubbles contained in the
oil. Consequently, the measurement of the sound velocity can be achieved
with good precision.
Example 5
This example is a sensor for determining whether an oil is synthetic oil or
mineral oil, by measuring the sound velocity of ultrasonic waves in the
oil. FIG. 9(a) shows an outline of a device of this example. This device
has a constitution consisting of a transducer for transmitting and
receiving ultrasonic waves, a temperature sensor for measuring the
temperature of oil at the time of sensing, a reflecting surface for
maintaining the propagation distance of ultrasonic waves at a constant
value, and an electronic circuit portion for measuring a propagation time.
Practically, the ultrasonic wave transmitting/receiving portion of the
transducer 3 is provided in an oil 6 that is contained in an oil pan 5. As
viewed in this figure, the ultrasonic wave transmitting/receiving portion
transmits ultrasonic waves perpendicularly to a reflecting surface 15,
independent of each other. Then, the ultrasonic wave
transmitting/receiving portion receives ultrasonic waves reflected
therefrom. Further, data representing a measured propagation time is
inputted to a propagation time measuring circuit 7. Thereafter, data is
outputted therefrom as those representing results of measurements
performed by a sound velocity measurement portion. Subsequently, oil
temperature information is inputted by a temperature sensor 4 to a
temperature measuring circuit 8 and a temperature correcting circuit 11.
Then, the sound velocity value is corrected according to the temperature
represented by the oil temperature information. Further, the kind of the
oil is determined or judged by an oil type judgement circuit 17.
This determining method is based on the fact that the values of the sound
velocity, which respectively correspond to the cases that the oil is
totally synthetic oil, that the oil is totally mineral oil and that the
oil is a mixture of synthetic oil and mineral oil, are different from one
another, as shown in FIG. 9(b). It is evident from this data that the kind
of oil can be determined by measuring the sound velocity value. Generally,
the volume elasticity and the density of oil varies with the type of oil.
Thus, a difference in the kind of oil results in a difference in the
measured value of the sound velocity of ultrasonic waves propagating
therethrough.
The synthetic oil and the mineral oil are different from each other in
characteristics such as a viscosity index, low-temperature performance,
and heat stability. Thus, these kinds of oil are different in service-life
warranty period from each other. It is, however, difficult to predict the
useful service-life warranty period of the mixture of these kinds of oil.
As a result of application of this example, this service-life warranty
period can be changed according to the kind of oil. Namely, in accordance
with a method of the present invention, the deterioration characteristics
and the useful service-life warranty period of the oil can be more easily
and simply changed with good accuracy by measuring the sound velocity of
ultrasonic waves in the oil.
In accordance with the sensor of the present invention, the alkalinity
corresponding to the degree of deterioration of oil can be simply and
easily detected by measuring the sound velocity of ultrasonic waves.
Moreover, simultaneously, the oil level can be detected by altering the
arrangement and combination of transducers. Furthermore, the
characteristics and the liquid surface level of gasoline can be detected
or determined by dipping the sensor of the present invention into a
gasoline tank.
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